This invention relates to a lighting system, particularly one that uses a centralized light source and one or more light guides or light conductors to transmit the light from the light source to a remote location. More particularly, a high brightness light source is envisioned for use in the automotive field where one or more light guides will direct light from the source to various end uses such as headlamps, turn signal indicator lamps, tail lights, interior lamps, etc.
As will be described, the present invention finds particular applicability in retrofitting a conventional halogen incandescent headlamp assembly by using a substantial number of existing components and modifying the assembly to take advantage of the benefits of the centralized lighting system. It will be understood, however, that the invention may be advantageously employed in related environments and applications such as display lighting arrangements or the like without departing from the scope and intent of the subject invention.
U.S. Pat. No. 5,278,731 of Davenport and Hansler (the '731 patent) is assigned to the same assignee as the present application. The '731 patent describes a related retrofit lighting system, the details of the '731 patent being incorporated herein by reference. Generally, it discloses use of a planar mirror that directs light from the output end of a light guide to a curvilinear reflective surface, such as a parabola. The planar mirror is located at or near the focus of the parabolic reflective surface so that collimated light is reflected from the parabolic surface. The light then continues toward a lens that closes the headlamp assembly and the lens directs the light in a desired manner.
Glare is always a concern with regard to light emanating from a headlamp. Particularly, light rays directed from the headlamp and upwardly into the eyes of an oncoming motorist are generally referred to as glare. Therefore, it is necessary to effectively control or handle light rays that would otherwise contribute to glare.
Still another concern in the headlamp environment is to provide as much forward directed light or "punch" as possible. Small angled prisms on the lens provide only a slight re-direction of the light without a substantial loss in the brightness so that light that passes through these portions provides the "punch" to the light pattern. Lenticules, the lens-like elements provided on the lens, spread the light to complete the desired light pattern.
Headlamp design must also take into consideration the configuration of the reflective surface so that light that exits the light guide is effectively and efficiently reflected forward by the reflective surface. The low profile and aerodynamic design of automobiles does not always provide for a symmetric parabolic reflective surface. In those instances where an asymmetric parabolic arrangement is used, the distance from the light source (end of the light guide) to the edges of the reflective surface are not equal. The different dimensions to the parabolic reflective surface edges also result in unequal image sizing. Accordingly, special consideration must be given to this arrangement.
With all of these constraints, it is still necessary to provide an interim, retrofit arrangement that uses many of the optical components of existing headlamp systems. Only selected portions of a centralized lighting system are incorporated into known arrangements to minimize the cost of eventually converting to a complete, centralized lighting system in the future.